Method and device for collecting, transporting, and delivering micro samples of blood

ABSTRACT

A method for collecting micro samples of arterial or venous blood from patients and for transporting and delivering such samples to suitable blood analysis equipment such as a conventional blood gas analyzer. An essential component of the device is a tubular elastomeric adapter-handle having integral body and tip sections, the body section having a tapered bore for receiving and holding the end portion of a heparinized glass microcapillary tube and the tip being both internally and externally tapered (in reverse directions) to permit releasable attachment of the tip to the hub of a hypodermic needle and, after a sample has been collected, to the inlet of a blood analyzer.

BACKGROUND AND SUMMARY

Arterial blood for diagnostic testing in blood gas analyzers is commonlycollected by means of syringes, vacuum tubes, or capillary tubes, eachof which presents substantial disadvantages and difficulties. Syringesmust be airtight and, if formed of glass, usually require lubrication.The entire dead space between the needle and the plunger must be filledwith a heparin solution, a procedure requiring considerable care toavoid small air bubbles that may cling to the barrel or to the plungerand prevent anerobic sampling. After collecting the blood, any residualair in the syringe must be expelled to prevent the loss of carbondioxide from the blood by diffusion.

Although arterial blood can also be collected in heparinized vacuumtubes, the requirement that such tubes be filled completely with blood(to avoid a loss of pCO₂ and an increase in pH) renders such a procedureespecially difficult. Also, there has been indications that utilizing avacuum for drawing blood samples may under some circumstances tend tocause hemolysis.

The use of heparinized capillary tubes has the advantage over the othertechniques of avoiding the collection of excessively large samples, aparticularly important consideration in pediatric studies, but in otherrespects the procedures used with such capillary tubes involve the sameproblems of collecting, transporting, and delivering samples undersubstantially anerobic conditions.

A main object of this invention therefore lies in providing a methodwhich greatly simplifies the procedures for sampling arterial (andvenous) blood, and for doing so in a way that minimizes risks ofexposure to air and increases the reproducibility and accuracy of testresults. Another object is to provide a relatively safe, uncomplicated,inexpensive, and highly effective method for drawing micro samples ofarterial or venous blood and for storing, transporting, and deliveringsuch samples to suitable blood analysis equipment.

Briefly, the device includes a capillary tube, an adapter-handledetachably connected to the tube, and a hypodermic needle detachablymounted on the adapter-handle. A protective cover may extend over theneedle, and at least one end cap is provided to seal the end (or ends)of the capillary tube after a blood sample is collected.

The adapter-handle is formed of resilient plastic material and hasintegral body and tip sections. A bore extends longitudinally throughboth sections with that portion of the bore within the body sectiontapering gradually inwardly at an angle of approximately 2 to 6 degreesmeasured from the axis of the adapter-handle. The tip of theadapter-handle has reduced outside cross sectional dimensions and istapered both internally and externally. The external taper is that of aconventional Luer taper, permitting the tip to be inserted and retainedwithin the hub of a standard hypodermic needle having a female Luertaper. The internal taper of the tip extends inwardly at an angle in therange of about 1 to 3 degrees and is dimensioned to receive andsealingly engage the inlet tubes of various models ofcommercially-available blood gas analyzers. Between the Luer-taperedouter surface of the tip and the gererally cylindrical outer surface ofthe body is a more sharply tapered surface of a frusto-conicalintermediate section, such surface being adapted to engage and sealagainst the mouths of the inlet passages of other types of availableblood gas analyzers.

In use, the heparin-coated capillary tube, the resilient adapter-handle,and the needle are assembled. A suitable artery or vein is punctured andthe capillary tube is filled by reason of arterial or venous pressure.The free end of the capillary tube is then capped, thereby preventingblood from escaping from either end of the capillary tube when theneedle is withdrawn from the puncture site. If analysis is to occurimmediately, then the user simply mixes the sample with the heparinwithin the tube, detaches and discards the needle, couples the tipportion of the adapter-handle to a blood analyzer, removes the cap, andallows the micro sample to be drawn into the analyzer. If, on the otherhand, any delay is to be encountered before analysis, the user detaches(and discards) the adapter-handle, replaces it with an end cap, andthen, following mixing, transit and/or storage, removes both caps,replacing one with a fresh adapter-handle for delivering the sample tothe inlet of a blood analyzer in the manner already described.

Other advantages, objects, and features of the invention will becomeapparent from the drawings and specification.

DRAWINGS

FIG. 1 is a side view of a device embodying this invention, the devicebeing shown with its needle cover removed (but with phantom linesshowing its attached position) for clarity of illustration.

FIG. 2 is an enlarged longitudinal side view, taken partly in section,of the device.

FIG. 3 is a still further enlarged fragmentary view of an indicatedportion of FIG. 2 illustrating the functional relationship between theparts.

FIG. 4 illustrates a first step in the method during which blood isdrawn into the microcapillary tube.

FIG. 5 illustrates a further step in which the needle is removed and thedistal end of the capillary tube is capped.

FIG. 5A depicts a further step which may be used when access to a bloodanalyzer is delayed.

FIG. 6 represents a further step of delivering the blood to an analyzerhaving a female connector forming the inlet thereof.

FIG. 6A depicts the delivery step when the analyzer is provided with amale connector at the inlet thereof.

DETAILED DESCRIPTION

Referring to the drawings, the numeral 10 generally designates a devicecomprising an adapter-handle 11, a needle assembly 12, and amicrocapillary tube 13. Such components may be supplied to the user inassembled form as shown, or they may be supplied as separate parts to beassembled by the user. In either case, a suitable cover 14 should beattached to the needle 12 to maintain sterility of the needle until use.An end cap 15 may be fitted upon the distal end of the capillary tube,and the entire assembly may be supplied in sterile condition within asuitable wrapper (not shown).

The needle assembly 12, shown most clearly in FIG. 2, is conventional inconstruction and includes a hollow needle 16 secured to a cup-shaped hub17. In the illustration given, hub 17 is formed of rigid plastic suchas, for example, polystyrene, although it is to be understood that othermaterials such as metals might be used. The open end of the hub providesthe entrance to a tapered cavity 18 dimensioned to receive andfrictionally engage the tip of adapter 11. The inward taper of thecavity 18 is commonly referred to as a standard Luer taper, meaning thatthe hub will mate tightly with a tapered syringe tip identified by thename of its originator. Such taper is described in Federal SpecificationGG-N-196 and corresponds to an angle approximately 1°43'6" measured fromthe axis of the needle assembly 12 (or an included angle of about3°26'12"). In a preferred embodiment, the metal needle 16 should be ofrelatively small gauge (No. 25 or less) and the opening at the mouth ofthe cavity should be approximately 0.165 of an inch in diameter.

The tubular needle cover 14 is entirely conventional and serves simplyto protect the pointed hollow needle 16 as well as objects which theneedle might otherwise contact, and to help maintain sterility of theneedle. The cover may be formed of any of a variety of rigid orsemi-rigid polymers such as, for example, polypropylene or otherpolyolefins.

The microcapillary tube is also conventional, being formed of glass andusually being of a standard length of 100 millimeters. Such a tube has athrough-bore which is precisely dimensioned to contain a sample ofpredetermined volume, ordinarily either 100 or 200 microliters (μl).Color coded bands 19 and 20 indicate to the user both the capacity ofthe tube and the fact that its interior surfaces have been heparinizedto prevent coagulation of a blood sample drawn into the tube.

End cap 15 is preferably formed of ethyl vinyl acetate, silicone rubber,or some other suitable resilient plastic material and defines a taperedcavity for snugly and sealingly receiving the end of glass capillarytube 13. While only a single end cap is needed in certain uses of theblood collection device, a second identical end cap may be supplied tothe user where temporary sealing of the opposite end of the capillarytube is also deemed necessary or desirable.

The adapter-handle 11 is also formed from a relatively soft resilientelastomer such as ethyl vinyl acetate or silicone rubber and is composedof integral body and tip sections 11a and 11b, respectively. A bore 21extends through the adapter with that portion 21a of the bore withinbody section 11a tapering gradually inwardly for receiving andfrictionally retaining one end of microcapillary tube 13. The gradualtaper of bore portion 21a and the resiliency of the material from whichthe adapter is formed not only insure that a tight frictional seal willbe formed between the end of the capillary tube and the adapter but alsopermits the adapter to form such engagement with standard capillarytubes of different diameters and capacities. It will be noted from theenlarged view of FIG. 3 that slight deformation of the wall of theadapter takes place when the end of a capillary tube is formed into thetapered bore portion 21a, such deformation assisting in the frictionalretention of the capillary tube without danger of chipping or fracturingthat tube. In addition, retention of a capillary tube by the adapter isenhanced by the squeezing force normally applied (in the direction ofarrows 22 in FIG. 2) when the resilient adapter is gripped between thefingers and used as a handle. The angle of taper x (FIG. 3) measuredfrom the longitudinal axis of the adapter should fall within 2° to 6°and should encompass a range of diameters of at least 0.08 to 0.10 of aninch. In a preferred embodiment, an angle of taper of 4° and a sizerange of approximately 0.070 to 0.110 of an inch have been foundeffective for coupling the adapter to standard microcapillary tubes.

In some cases it may be desirable to draw a larger sample of arterial orvenous blood and for that purpose the tapered bore of the body section11a may be stepped outwardly to provide an enlarged entrance portion21b. Bore portion 21b has a Luer taper similar to that of hub cavity 18and, consequently, is adapted to mate with the Luer tip of a standardsyringe. Like the cavity 18 of the needle hub, bore portion 21b shouldhave a maximum diameter at its mouth of approximately 0.165 of an inch.

The tip section 11b of the adapter is reduced in outside dimensions andhas a standard male Luer taper allowing the distal portion of the tip tobe received tightly within the cavity 18 of the needle hub. The angle oftaper of the tip's outer surface should match closely the angle ofinside taper of the hub with the maximum outside diameter of the tip atpoint 23 exceeding the inside diameter at the mouth of cavity 18. Adifferential of at least 0.003 of an inch should be provided (0.005preferred) to insure a snug fluid-tight friction fit between the parts.

Beyond the Luer tapered outer surface, between point 23 and thegenerally cylindrical outer surface of body section 11a, the tip isprovided with a flared or frusto-conical outer surface 24. The angle ofthat frusto-conical surface, measured from the axis of the adapter,should fall within the general range of 10° to 30°, an angle ofapproximately 20° being found particularly effective. As describedhereinafter, the frusto-conical surface is not merely a transitionalsurface between the Luer taper of the tip and the cylindrical surface ofthe body; it provides an inclined stop for limiting the extent ofinsertion of the adapter into the inlet port of a blood analyzer, andfor sealingly engaging that port when delivery of a sample to such ananalyzer takes place.

It will be noted that the internal and external longitudinal surfaces ofthe tip section 11b are reversely tapered; that is, in addition tohaving a Luer taper along its outer surface the tip has areversely-tapered bore portion 21c which gradually and progressivelyincreases in size towards the free end of the tip section. The angle oftaper y (FIG. 2) should fall generally within the range of 1° to 3°measured from the longitudinal axis of the adapter, the preferred angleof taper being approximately 2°. At its mouth the bore portion 21cshould have a diameter of at least 0.08 of an inch, a preferreddimension being about 0.09 of an inch. As shown, bore portion 21c taperssmoothly and gradually inwardly to merge with bore portion 21a of bodysection 11a.

For use, the device 10 may be supplied in assembled condition as shownin FIG. 1. Alternatively, the device may be supplied in disassembledcondition, requiring interfitting of the major components by the user.Assuming that the device is in the assembled condition of FIG. 1, theuser removes end cap 15, detaches the protective needle cover 14, and,holding the device by means of the resilient adapter-handle 11, insertsthe sterile needle 16 into the blood vessel from which the sample is tobe taken. For blood gas analysis arterial blood is preferred. Such bloodmay be obtained by inserting the fine-gauge needle 16 into an arterysuch as the brachial, radial, femoral, or jugular arteries. FIG. 4depicts the sampling step, the outline of the patient's body beinggenerally represented by line 25 and the transparent collection tubeshown to be filled with blood taken from the patient. Entry of theneedle into an artery is confirmed by the pulsatile filling of the boreof the glass capillary tube, such filling action generally beingcompleted within three seconds and occuring by reason of arterial (orvenous) pressure. The user then withdraws the needle and immediatelycaps the remote end of the capillary tube with cap 15 (FIG. 5). Stillholding the device by means of the adapter-handle, the user detaches(and discards) the needle assembly 12. If the blood analyzing equipmentis close at hand, the adapter is then simply coupled to the inletconnector of the analyzer to allow the collected blood sample to bedrawn into the analyzer where it is tested (FIGS. 6 and 6A).

After taking a sample, and before introducing that sample into ananalyzer, a user should make sure that the sample is thoroughly mixedwith the heparin salt coating the inside surfaces of the capillary tube.A suitable magnetic stirrer, commonly referred to as a "flea", may beinserted into the bore of the tube and reciprocated therein by means ofan external magnet. Particularly effective results may be achieved whereend cap 15 is formed and used as set forth in my copending U.S. Pat.application Ser. No. 10,234, filed Feb. 8, 1979, the disclosure of whichis incorporated by reference herein, so that upon completion of themixing step the flea may be captured and removed by means of the cap,thereby preventing the possibility that such a flea might be left withinthe capillary tube and be drawn accidentally into the blood analyzer.

In FIG. 6 the numeral 26 generally designates that type ofcommercially-available blood analyzer having an inlet port 27, the mouthof which is engagable with the tip section of the adapter 11 to providea temporary seal as the blood sample is aspirated from the capillarytube into the machine. The frusto-conical outer surface 24 of theadapter is particularly effective in forming such a seal with the mouthof the instrument and for limiting the extent of insertion of theresilient adapter into the inlet.

FIG. 6A schematically depicts a different type of blood analyzer 26' inwhich the inlet takes the form of a protruding nipple or tube 28 havingan outside diameter of approximately 0.08 of an inch. In delivering ablood sample to such an analyzer, the user, holding the device by itsresilient adapter 11, simply fits the internally tapered tip section 11bon to the inlet tube 28 and allows the blood sample to be drawn into themachine.

In those cases where the blood analyzer is remote from the collectionsite, adapter-handle 11 may be removed from the filled capillary tube 13and replaced by a second end cap 15 (FIG. 5A). With both ends of thecapillary tube so capped, the collected sample may be mixed,transported, and temporarily stored under refrigeration. Upon arrival atthe blood analyzer, one of the end caps is removed and replaced by afresh adapter 11. The procedure represented in FIG. 6 or 6A is thenperformed with the distal end cap 15 removed from the capillary tube topermit aspiration of the blood sample into the analyzer.

It is believed evident from the foregoing that the adapter 11 isconstructed to perform a multiplicity of functions. In addition to itscoupling functions the adapter serves as a resilient handle. In theoperations depicted in FIGS. 4, 5, 6, and 6A, the user grips thesampling device by holding the resilient adapter between his fingers. Asalready described, the squeezing forces tend to assist in maintainingthe capillary tube and adapter in interconnected relation. In addition,the danger of breakage of the fragile capillary tube, and the risks ofpossible contamination of the user, are reduced. For example, should apatient move suddenly during arterial or venous puncture, the resilienthandle provides limited articulation between the rigid glass tube 13 andthe needle assembly 12, thereby reducing the chances of breakage ofeither rigid part, and, should such breakage happen to occur, the handleserves as a protective sheath between the fractured tube and the user'sfingers to prevent injury and possible contamination.

While in the foregoing I have disclosed an embodiment of this inventionin considerable detail for purposes of illustration it will beunderstood by those skilled in the art that many of these details may bevaried without departing from the spirit and scope of the invention.

I claim:
 1. A method for collecting a micro sample of blood anddelivering the same to an analyzer for laboratory analysis, using anopen-ended heparinized capillary tube having one end received within thebore of a tubular adapter, said adapter having a tip with a male Luer,and a hypodermic needle having a hub with a female Luer taperfrictionally and releasably receiving said adapter tip, comprising thesteps ofinserting said needle into a blood vessel of a patient andcollecting a sample of blood in said capillary tube, disconnecting saidneedle hub from said adapter and capping the end of said capillary tuberemote from said one end thereof, and then coupling said adapter to theinlet of a blood analyzer and removing said cap from said capillary tubeto allow the blood sample to flow from said tube into said analyzer. 2.The method of claim 1 in which said coupling step is performed byintroducing said tapered tip of said adapter into an inlet opening of ablood analyzer to form a fluid-tight seal therebetween.
 3. The method ofclaim 1 in which the bore of the tip of said adapter has a female taper,said coupling step being performed by inserting an inlet tube of a bloodanalyzer into the bore of said tip to form a fluid-tight sealtherebetween.
 4. The method of claim 1 in which said needle is insertedinto an artery.
 5. The method of claim 1 in which said needle isinserted into a vein.
 6. The method of claim 1 in which said adapter isformed of resilient, flexible plastic material and in which saidinserting, disconnecting, and coupling steps include gripping saidadapter between a user's fingers, thereby increasing the contact forcebetween said adapter and said capillary tube.
 7. A method for collectinga micro sample of blood and delivering the same to an analyzer forlaboratory analysis, using an open-ended heparinized capillary tubehaving one end frictionally received within the bore of a tubularadapter, said adapter having a tip with a male Luer taper, and ahypodermic needle having a hub with a female Luer taper frictionally andreleasably receiving said adapter tip, comprising the steps ofinsertingsaid hypodermic needle into a blood vessel of a patient to fill saidcapillary tube with a sample of the patient's blood, withdrawing theneedle from said vessel and capping the end of said capillary tuberemote from said one end to retain said sample within said tube,transporting said sample to a blood analyzer in said capped capillarytube, and thereafter uncapping said tube and discharging said sampleinto said analyzer.
 8. The method of claim 7 in which said sample isdischarged into said analyzer by coupling said tip of said adapter tothe inlet of the analyzer to place said capillary tube in flowcommunication with said inlet.
 9. The method of claim 7 in which thereis the further step of disconnecting said adapter from said one end ofsaid capillary tube prior to said transporting step.
 10. The method ofclaim 9 in which there is the further step of capping said one end ofsaid capillary tube after said needle is disconnected therefrom andprior to said transporting step.
 11. The method of claim 9 in whichthere is the further step of attaching a second adapter to said one endof said capillary tube after said transporting step, said sample beingdischarged into said analyzer by coupling said second adapter to theinlet of said analyzer.